Sanitation and waste water systems are becoming increasingly expensive to operate and face daunting environmental, community and regulatory pressures. Agencies and organizations that manage sanitation systems face complex and costly problems. Three of the main problems facing sanitation system operators are sewage spills, treatment failure, and illegal dumping. The first two of these problems often result in uncontrolled spills of septic materials into the environment, causing environmental damage, health risks, and high cleanup and mitigation costs, while the third problem respectively generates a potential danger to treatment systems, the environment and uncontrolled liability for the sanitation operators.
Sewage spills are becoming more common and more costly for agencies and organizations that are responsible for handling waste disposal and treatment. Increased population is putting severe strain on sewage systems, systems are aging and becoming more susceptible to leaks and spills, and costs of spills which include clean-up, mitigation and fines by regulatory agencies are skyrocketing. A recent market analysis by the civil engineering firm of Brown and Caldwell entitled “What's a Spill Worth?, or a Brief Look at Community Values” surveyed 676 sewage agencies in California to capture the economic value of avoiding spills. The results of the survey revealed, for example, for spills on the order of 1000's of gallons, agencies were willing to spend $10 per gallon to avoid these spills. For larger spills, agencies were willing to spend $500,000 to more than $1 million to avoid spills reaching receiving waters such as rivers, lakes or the ocean. It is not uncommon for sanitation agencies to be fined millions of dollars for sewage spills, especially if they are large or reach receiving waters. Sewage spills also create serious public relations problems for operating agencies, and it is not uncommon for sewage to back up into residences and commercial facilities, creating serious liabilities for the agencies and very costly and time consuming clean-up.
Sewage spills are caused by many problems, but three primary causes are often cited: grease buildup from illegal discharges by restaurants, other commercial businesses or residences that use fat, lard or grease in food or industrial processing; structural problems in sewage pipes caused by the intrusion of plant roots or pipe breakages that are often exacerbated by objects such as rags that are thrown into the sewer; and “infiltration and inflow”, overflows caused by leaks into the system that often occur during times of high rainfall or runoff. Sewage spills often begin, then, with sewage pipes that are either blocked or are at capacity and overflowing due to high flows. Currently there is no practical early warning system to provide system operators a cost-effective means to prevent a spill before it happens. Typically spills are detected by the community though serendipitous observation of water flowing out of manholes or odors around wet areas of ground around or above sewage lines. By the time sewage spills are noticed by the public, it is too late—the spill has already occurred, and it is just a question of how much sewage has spilled into the environment, whether the spill has reached clean receiving waters, how much it will cost and how long it will take to clean-up the problem and how large the fines will be.
A second major problem for sanitation agencies is a loss of treatment due to the killing off of beneficial treatment bacteria at the sewage treatment plant. A common part of the treatment process is the use of bacteria to naturally decompose organic materials in the waste water. If incoming waste is toxic to the beneficial bacteria, a massive die-off can occur without warning, and sewage can be spilled or otherwise discharged that is unknowingly under-treated or untreated. A means to provide an early warning of toxic materials that are traveling through the sewage collection system to the treatment plant could provide operators with the option of diverting the incoming flow into a holding pond until the slug of toxic material has dissipated would be useful and important to the sanitation industry. In addition, if the source of the toxic materials could be identified, the source could be stopped or fined as appropriate.
In addition, illegal dumping of materials into manholes is a common problem. The source could be illegal operations of commercial establishments that face large costs associated with disposal of hazardous waste, including dumping of trucked sewage and septic pumping, or simple vandalism. Covert dumping of illicit drug lab waste is an additional source of problems. Rather than pay high fees at legal dumping stations, truckers of hazardous waste, include septic waste, could access a remote manhole illegally and dump large quantities of materials with low probability of detection and prosecution. Such uncontrolled dumping into sewage systems is a major problem for the sanitation industry because the sewage system operators are ultimately responsible for what is dumped into their systems and the operators have little or no chance of catching or preventing illegal dumping.
Illegal access to manholes has forced some sanitation agencies to weld down their manholes, creating a significant deterrent to illegal access, but at the same time causing operational problems, including delayed or deferred maintenance or in the case of an emergency, significant delay in accessing a manhole through the manhole cover.
Current methods exist for the monitoring of level and flow in manholes, for example, two such products are the Hach (Loveland, Colo.) Sigma 1000 and the Marsh-McBirney Flo-Dar systems. These methods suffer from one or more of the following problems: (a) installation requires entry into the manhole, thus high cost and higher safety risk from entering the manhole; (b) the system requires wired communications, thus trenching around the manhole; (c) the system requires continuous 120 Volt AC power, thus trenching around the manhole; (d) the total installation is costly, limiting the deployment of these systems to no more than a few select manholes. A small municipality may have 5,000 to 10,000 manholes, and large municipality may have more than 100,000 manholes. In order to provide wide coverage, the total cost per manhole must be reasonable.
It is clear that a distinct need exists for a low cost, robust system and method to provide an early warning system to avoid many of the problems and costs that sanitation system operators face. Such as system should be inexpensive so that it can be widely deployed, provides wide area communications, and is rapid enough to give operators time to respond and prevent catastrophic failure before it occurs and affects the community and the environment. This system can also be a platform for a variety of sensors, for a variety of applications, including intrusion alarms, closed space monitoring for example for gases, water quality monitoring, traffic monitoring, and environmental or pollution monitoring, and by virtue of distribution in a wide coverage urban area, such a system can have multiple uses in addition to manhole monitoring.